Rotary speed responsive switch device



May 8, 1962 W. J. THOMPSON ROTARY SPEED RESPONSIVE SWITCH DEVICE Filed March 22, 1960 Iqm' x i \r w 1-4 I N (\l I a I! V N o N\ E I. (k LL 1. Q a g :e R Q g I INVENTOR I q 1 V l/V/LL/AM J THOMPSON BY 0 Q "3 a 2 v ATTO NEW y 1962 w. J. THOMPSON 3,033,954

ROTARY SPEED RESPONSIVE SWITCH DEVICE Filed March 22, 1960 2 Sheets-Sheet 2 IN VENTOR WILL/AM J THOMPSON ATTO NE Y United States. Patent 3,033,954 ROTARY SPEED RESPONSIVE SWITCH DEVICE Wiliiam J. Thompson, Cold Spring Harbor, N.Y., assignor to Sperry Rand Corporation, Great Neck, N.Y., a corporation of Delaware Filed Mar. 22, 196i Ser. No. 16,730 4 Claims. (Cl. fill-80) This invention relates to a device for actuating a switch in response to the rotary speed of a rotating body.

The present invention is an improvement over prior art devices of this type primarily because the center of gravity of the speed responsive element does not undergo a change in relative position during operation of the device. The operation of the device is independent of linear vibrations and may be subjected to high external acceleration forces without effecting the operation of the device. Further, the device is relatively simple mechanically, rugged and capable of accurate operation under severe vibration conditions while at the same time it may be designed to be extremely small and light weight. Further, it is capable of being designed to operate over an unusually wide range of speed.

It is a primary object of the present invention to provide a rotary speed responsive switch device that is operable under adverse environmental conditions.

It is a further object of the present invention to provide a rotary speed responsive device that is operable to provide actuation of a switch at a predetermined rotary speed which is simple, compact and reliable under adverse operating conditions, particularly, severe vibration.

The above objects are achieved by the rotary speed responsive switch device of the present invention which comprises a support member, a rotatable body mounted for rotation with respect to said support member, a switch ring mounted on said support member and forming one contact of an electrical switch, a wobble ring mounted on said support member for pivotal movement about two perpendicular axes and forming the other contact of the electrical switch, said wobble ring being cooperative with said switch ring, and an actuating arm mounted on said rotating body and rotatable therewith tending to sequentially depress elemental portions of said wobble ring in accordance with the rotary speed of said body whereby below a predetermined rotary speed of said body the wobble ring is in a first predetermined condition and at said predetermined rotary speed of said body the wobble ring is in a second predetermined condition for effecting the operation of said switch.

Referring to the drawings,

FIG. 1 is a sectional view of a preferred embodiment of a normally-open rotary speed responsive switch device of the present invention;

FIG. 2 is an end view partially in section of the device of FIG. 1 taken along lines 22 thereof;

FIG. 3 is an alternative embodiment of a normallyclosed rotary speed responsive switch device of the present invention;

FIG. 4 is an end view partially in section of the device of FIG. 3 taken along lines 44 thereof; and

FIG. 5 is a schematic 'end view of the device of FIG. 3 taken along lines 44 for illustrating the operation thereof.

Referring to FIGS. 1 and 2, a rotating body in the form of a shaft is mounted for rotation about an axis 11 with respect to a fixed, non-conductive support member 12 by means of spaced bearings 13 and 14. The shaft 10 is rotated by means not shown. A disc 15 is connected to an extremity of the shaft 10 for rotation therewith about the axis 11. At a point near the periphcry of the disc 15 a depressor element in the form of a screw 16 is threadedly connected to project through the 3,033,954 Patented May 8, 1962 disc 15. Preferably, the screw 16 is plastic and has one extremity rounded to provide substantially point contact where it abuts against a circular conductive wobble ring 20. The other extremity of the screw 16 is slotted in order that it may be manually screwed in and out of the disc 15 for varying the distance which the screw 16 projects beyond the disc 15 which in turn varies the amplitude of the wobble in a direction parallel to the axis 11 introduced ,to the wobble ring 20, in a manner to be more fully explained.

The wobble ring 24) is pivotally mounted to wobble but is prevented from rotating around the axis 11, by means of a circular gimbal 21 and pivots 22, 2A2, 23 and 23. The gimbal 21 is mounted on the fixed support member 12 for pivotal movement about an axis 24 by means of the spaced pivots 22 and 22'. The wobble ring 20 is in turn mounted on the gimbal 21 for pivotal movement about an axis 25 by means of the spaced pivots 23 and 23'. The axes 2-4 and 25 are mutually perpendicular with respect to each other and with respect to the axis 11 at a point 26. Thus, the wobble ring 20- is free to wobble in all quadrants defined by the axes 24 and 25 but is constrained from rotating around the axis 11. By this arrangement, the center of gravity of the wobble ring 2% at point "26 remains fixed at this point;

30 forms one contact of an electrical switch while the other contact is formed by the wobble ring 20. With the shaft 19 at rest, the wobble ring 20 and the switch ring 30 are spaced with respect to each other and are out of contact with each other as shown in FIG. 1 thereby forming a normally-open switch device.

Four helical springs 31, 32, 33 and 34 are disposed apart around the periphery of the wobby ring 20 and each has an extremity connected to the wobble ring 29 and another extremity connected to the support member 12. An electrical lead 35 connects to one extremity of the helical spring 31 thereby providing electricity to the wobble ring 2i? through the spring 31. An electrical lead 36 connects to the switch ring 30 on the side opposite that facing the wobble ring 20 thereby providing electricity to the switch ring 30. The leads 35 and 36 may be connected to a source of electrical energy not shown.

A housing comprising a base 40 and a cover 41 may enclose the aforementioned elements to prevent contamination thereof. The base 40 may also be provided with screw holes as shown in FIG. 2 for attachment to a chassis not shown.

In operation, with the shaft 10 at rest, the screw 16 abuts against the wobble ring 20 and causes the wobble ring 20 to assume the canted position shown in FIG. 1 with the spring 31 compressed and the spring 33 extended. The electrical switch is open since the wobble ring 20 does not contact the switch ring 39. As the shaft 10 begins to rotate, only the disc 15 and the screw 16 rotate with it while all the elements mounted on the fixed support member 12 remain stationary except for wobble of the wobble ring 2% As the screw 16 rotates and rubs against the wobble ring 20, the screw 16 causes wobble or mutation of the wobble ring 20 by sequentially depressing elemental portions of the wobble ring 20. The amplitude of the wobble of the wobble ring 20 in a direction parallel to the axis 11 as determined by the the wobble ring 20 contacts the switch ring 3%) thereby closing the electrical switch. The large deflections of the wobble ring 21} at the resonant condition cause it to continuously contact the switch ring 39 thus maintaining the switch closed.

This condition of continuous contact between the wobble ring 24} and the switch ring 30' is maintained for speeds above resonance. At resonance the wobble motion is provided as explained previously and the point of con,- tact between the screw 16 and the Wobble ring 20 leads the electrical contact point between the wobble ring 29 and the switch ring 3t by a substantially constant angle of slightly less than 90. As the screw 16 rotates, it continually exerts a force normal to the wobble ring 20 at its point of contact with the wobble ring 20. This nor: mal force at any instant of time tends to depress the wobble ring 20 and at and above resonance tends to rotate the wobble ring 29 about its electrical point of contact with the switch ring 30 which electrical point of contact is itself continuously rotating. Above resonant speeds this normal force increases as required to accelerate the wobhis motion and overcome inertia of the Wobble ring 20 by means of the rigid construction of the disc and the screw 16. Thus, the desired switching action is accomplished with the switch open below a predetermined rotary speed of the shaft It and the switch closed above a predetermined rotary speed of the shaft 11a.

Although FIG. 1 shows for purposes of explanation the Wobble ring canted at an appreciable angle, in actual practice it has been found that the wobble induced by the screw 16 should be relatively small and the air gap between the contacts should be comparatively large in order that contact between the wobble ring 20 and the switch ring 3% is made only at and above resonance and does not occur due to wobble occurring before resonance. It will be appreciated that as the wobble ring 20 wobbles, its center of gravity at point 26 is not subject to change in relation to the rest of the mechanism, therefore it is not affected by linear vibrations thus permitting the device to be used Where severe vibrations are encountered without undesirable intermittent operation. Further, in practice it has been found that utilizing a plastic screw 16 with a leaded Phosphor bronze wobble ring 20 and a sterling silver plated switch ring 30 has resulted in very little wear occurring. The device can be made extremely compact and light weight, for example, successful results have been obtained from devices as small as an inch and one-quarter in diameter.

Referring now to FIGS. 3 and 4, an alternative embodiment of the device will be described incorporating the principles of the present invention with respect to a normally-closed switch. Like parts are indicated by like reference characters and for purposes of simplicity only the new elements will be described.

A bracket 50 is threadedly connected to an extremity of the shaft 10 for rotation therewith. Mounted on the bracket 50 for providing a resilient force against the pe riphery of the wobble ring 20 is a spring member 51 having a plastic depressor 52 mounted thereon for abutting against the Wobble ring 20. Preferably, the member 51 is a flat circular spring having a central opening 53 which permits the shaft 10' and portions of the support member 12 to project theret-hrough. The spring 51 is connected to the bracket Si by means of rivets 55- or other suitable connecting means. The magnitude of the applied resilient force may be varied by positioning the bracket 50 on the threaded end of the shaft 10 along the axis 11. The bracket 50 is locked in place by means of a con ventional split yoke and screw arrangement.

As described above with respect to the embodiment of FIG. 1, the wobble ring 20 forms one contact of an elec- 4 trical switch while the other contact is formed by the Switch ring 30, the latter receiving electricity through the lead 36 which is connected thereto. Electricity is supplied to the wobble ring Ztl by means of the lead which in this embodiment is connected to a conductive ring 54 that is securely mounted on the non-conductive support member 12 and forms the supporting structure for the pivots 22 and 22. Electricity is privided to the wobble ring 20 by means of lead 35, ring 54, pivots 2 2 and 212', gimbal 21 and pivots 23 and 23'.

In this embodiment, the wobble ring 20 contacts the switch ring 30 due to the resilient force applied by the spring 51 and the depressor 52 thus maintaining the electrical switch closed when the shaft 10 is at rest or below a predetermined rotary speed. As the shaft Ill begins to rotate, the depressor 52 rotates with it and tends to sequentially depress elemental portions of the wobble ring 20 causing the wobble ring 20 to contact the switch ring 30 during 360 of rotation of the shaft 10.

As shown in FIGS. 3 and 5, at very low rotary speeds of the shaft 10, the location of the point of contact A of the depressor 52 on the wobble ring 23 substantially coincides with the point of contact B between the wobble ring 2% and the switch ring 30. At higher rotary speeds of the shaft 10, the point of contact A of the depressor 52 leads the point of contact B between the wobble ring 20 and the switch ring 30 due to the inertia of the wobble ring 20.. For example, with the shaft Ill rotating at a relatively high speed in a clockwise direction as shown in FIG. 5 and the depressor 52, as shown in dotted lines, contacting the wobble ring 20 at point A, the contact point B of the wobble ring 20 and the switch ring 30 lags the point A by approximately 45 because the in-. ertia of the wobble ring 20 prevents it from following what are effectively the impulses of the spring loaded dcpressor 52.

At a predetermined rotary speed of the shaft 16, the inertia of the wobble ring 20 prevents it from following the action of the depressor 52 to such an extent that the wobble ring 20 does not contact the switch ring 3d during a complete revolution of the shaft 10. At this critical speed with the Wobble ring 20 entirely out of contact with the switch ring 30, the electrical switch is opened thereby providing a normally-closed rotary speed sensitive switch that opens and remains open above a predetermined critical speed. The inertia of the mass 20 and the resilient force applied by the spring loaded depressor 52 are designed to provide the desired action at the predetermined critical speed.

The normally-closed switch of FIG. 3 includes all of the advantages described above with respect to the device of FIG. 1.

While the invention has been described in its preferred embodiments, it is to be understood that the words which have been used are words of description rather than of limitation and that changes within the purview of the appended claims may be made without departing from the true scope and spirit of the invention in its broader aspects.

What is claimed is:

1. A device which is operably responsive to the rotary speed of a body to. actuate a switch, comprising a support member, said body being mounted for rotation with respect to said support member about an axis of rotation, a first circular element of conductive material mounted on said support member and forming one contact of said switch, a second circular element of conductive material cooperative with said first element and forming the other contact of said switch, means including gimbal means mounted on said support member and pivotally supporting said second element for pivotal movement about two mutually perpendicular axes that are also perpendicular to said axis of rotation, and actuating means mounted for rotation with said rotating body tending to sequentially depress elemental portions of said second element in accordance with the rotary speed of said body whereby below a 5 predetermined rotary speed of said body the second element is in a first predetermined condition and at said predetermined rotary speed of said body the second element is in a second predetermined condition for effecting the operation of said switch.

2. A device which is operably responsive to the rotary speed of a body to actuate an electrical switch, comprising a support member, said body being mounted for rotation with respect to said support member about a first axis, a switch ring mounted on said support member and forming one contact of an electrical switch, a wobble ring, said wobble ring forming the other contact of the electrical switch and being cooperative with said switch ring, means including gimbal means mounted on said support member and pivotally' supporting said wobble ring for pivotal movement about two mutually perpendicular axes that are also perpendicular to said first axis, and actuating means mounted for rotation with said rotating body tending to sequentially depress elemental portions of said wobble ring in accordance with the rotary speed of said body whereby below a predetermined rotary speed of said body the wobble ring is in a first predetermined condition and at said predetermined rotary speed of said body the wob- 6 ble ring is in a second predetermined condition for effecting the operation of said switch.

3. A device as claimed in claim 2 wherein said actuating means is resiliently mounted on said rotating body and applies a resilient force against said wobble ring wherein in said first predetermined condition said wobble ring contacts said switch ring and in said second predetermined condition the inertia of said wobble ring prevents it from following the resilient force applied by said actuating means to an extent that said wobble ring does not contact said switch ring.

4. A device as claimed in claim 2 including resilient means connected to said support member and said wobble ring for preventing said wobble ring from contacting said switch ring at said first predetermined condition, and at said second predetermined condition the natural frequency of the wobble ring and the resilient means causes said wobble ring to contact said switch ring.

References Cited in the file of this patent UNITED STATES PATENTS 

